Rare earth-iron-boron sintered magnets

Abstract

Permanent magnets are prepared by method comprising mixing a particulate rare earth-iron-boron alloy with a particulate transition metal, aligning the magnetic domains of the ixture, compacting the aligned mixture to form a shape, and sintering the compacted shape.

What is claimed is: 
     
       1. A composition for preparing permanent magnets comprising: (a) a particulate alloy containing iron, boron, and at least one light rare earth metal, said particulate alloy comprising a main magnetic phase having an empirical formula of about RE 2  (Fe+Co) 14  B, and   (b) at least one particulate metal additive consisting essentially of a heavy lanthanide metal.   
     
     
       2. The composition defined in claim 1, wherein the alloy comprises neodymium. 
     
     
       3. The composition defined in claim 1, wherein the alloy further contains a ferromagnetic metal selected from the group consisting of cobalt, nickel, and mixtures thereof. 
     
     
       4. The composition defined in claim 1, wherein the particulate metal additive contains dysprosium metal. 
     
     
       5. The composition defined in claim 1, wherein the particulate alloy comprises neodymium and has the nominal empirical formula of Nd 15  B 8  Fe 77  and the amount of the particulate metal additive comprises about 0.5 to about 10 weight percent of the composition. 
     
     
       6. The composition defined in claim 1, wherein the amount of the particulate metal additive comprises about 0.5 to about 10 weight percent of the composition. 
     
     
       7. A composition for preparing permanent magnets comprising: (a) a particulate alloy containing iron, boron and neodymium metal; and   (b) at least one particulate transition metal additive containing a single heavy lanthanide metal selected from the group consisting of gadolinium, holmium, dysprosium, and terbium.   
     
     
       8. The composition defined in claim 7, wherein the alloy further contains a ferromagnetic metal selected from the group consisting of cobalt, nickel, and mixtures thereof. 
     
     
       9. The composition defined in claim 7, wherein the particulate alloy has a nominal empirical formula of Nd 15  B 8  Fe 77  and the amount of the particulate metal additive comprises about 0.5 to about 10 weight percent of the composition. 
     
     
       10. The composition defined in claim 7 wherein said particulate alloy comprises a main magnetic phase having an empirical formula of about Nd 2  Fe 14  B. 
     
     
       11. A composition for preparing permanent magnets comprising: (a) a particulate alloy containing at least one rare earth metal, iron, boron, and a ferromagnetic metal selected from the group consisting of nickel, cobalt, and mixtures thereof, and   (b) at least one particulate metal additive consisting essentially of a single heavy lanthanide metal selected from the group consisting of gadolinium, holmium, dysprosiium, and terbium.   
     
     
       12. The composition defined in claim 11, wherein the particulate alloy comprises neodymium and has the nominal empirical formula of Nd 15  B 8  Fe 77  and the amount of the particulate heavy lanthanide metal additive comprises about 0.5 to about 10 weight percent of the composition. 
     
     
       13. The composition defined in claim 11 wherein said particiulate alloy comprises a main magnetic phase having an empirical formula of about Nd 2  (Fe+Co) 14  B.